The present disclosure generally relates to methods and related configurations, components and assemblies of repairing cracks in ceramic matrix composites (CMCs), and in particular repairing matrix cracks in fiber-reinforced melt infiltrated ceramic matrix composites (MI-CMCs).
Monolithic ceramics, such as SiC ceramics, were developed many years ago but never found their way into high temperature structural applications because they lack damage tolerance and they fail catastrophically. Ceramic matrix composites (CMCs), particularly those reinforced with fibers, were developed to alleviate the damage tolerance issues of monolithic ceramics and thereby have become attractive for high temperature structural applications, such as in gas turbine engines. One type of fiber-reinforced CMCs that is particularly attractive for high temperature structural applications is reactive melt infiltrated fiber-reinforced CMCs (hereinafter ‘MI-CMCs”).
In MI-CMCs, a preform of fibers and matrix constituents is infiltrated with a metal which produces a ceramic matrix when reacting with the matrix constituents. SiC-based MI-CMCs, wherein the infiltrating metal is silicon or a silicon alloy and the matrix constituents are such that the resulting matrix is substantially SiC (e.g., SiC and/or C particulates), are particularly attractive for high temperature structural applications because of their high thermal conductivity, excellent thermal shock resistance, creep resistance, and oxidation resistance compared to other CMCs.
One current disadvantage of MI-CMCs is that they are relatively expensive, and therefore MI-CMC components need to be in working condition for extended periods of time to be economically viable. For example, in gas turbine applications MI-CMC components are expected to last through several engine service intervals. Unfortunately during use in typical high temperature structural applications (e.g., gas turbine applications) MI-CMC components are often subjected to loads above the matrix cracking stress of the components. The resulting cracks in the matrix portion of the components from such stresses act to decrease the stiffness and oxidation resistance of the MI-CMC composite, and can lead to premature failure of the MI-CMC component. Further, temporary overstress conditions, such as from dropped parts or tools, can occur during MI-CMC component fabrication, transportation and/or installation and also can result in matrix cracks.
As a result, a need exists for methods and related configurations, components and assemblies for repairing matrix cracks in MI-CMC components to restore them to a usable condition.